Apparatus for controlling air cylinder stroke motions



G. w. EMRICK Nov. 4, 1952 APPARATUS FOR CONTROLLING AIR CYLINDER STROKEMOTIONS 3 Sheets-Sheet 1 Filed April 1'7, 1948 wig 4 m w Z W//IIIIUIIIIIIIIIIIIIII INVENTOR GEORGE W. EMRICK ATTORN Y NOV. 4, 1952 Iw, EMR|K 2,616,398

APPARATUS FOR CONTROLLING AIR CYLINDER STROKE MOTIONS Filed April 17,1948 3 Sheets-Sheet 2 59 I I 26 O :2

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I INVENTOR GEORGE W. EMRICK v ATTORNEY G. W. EMRICK Nov. 4, 1952APPARATUS FOR CONTROLLING AIR CYLINDER 'STROKE MOTIONS Filed April 1'7,1948 3 Sheets-Sheet 3 INVENTOR GEORGE W. EMRICK ATTORNEY Patented Nov.4, 1952 UNITED STATES PATENT OFFICE APPARATUS FOR CONTROLLING AIRCYLINDER STROKE MOTIONS George W. Emrick, Forest Hills, N. Y.;Manufacturers Trust Company executor of said George W. Emrick, deceasedApplication April 17, 1948, Serial No. 21,665

10 Claims.

This invention relates to apparatus employing an air cylinder, with apiston operating in the cylinder with automatic means controlling thestroke or movement of the piston in the cylinder in controlling varioustypes and kinds of feed motions in machines of various kinds. Still moreparticularly, the invention deals with apparatus of the characterdescribed wherein a solenoid actuated valve is employed forautomatically controlling air flow to the cylinder in control of thestroke or movement of the piston in the cylinder. Further, the inventiondeals with apparatus of the character described having means controllingthe speed of the piston stroke so as to provide in a definite pistonstroke or movement, piston operation at two different speeds.

broken away.

Fig. 2 is a plan view of the structure seen in Fig. 1, showing thecasing in section, with part of the structure broken away.

Fig. 3 is a section on the line 3-3 of Fig. 2, on an enlarged scale andomitting part of the construction.

Fig. 4 is a section on the line 4-4 of Fig. 3, showing only the valvemechanism, and with part of the construction shown in elevation.

Fig. 5 is a section substantially on the line 5-5 of Fig. 4, with partof the construction shown in elevation.

Fig. 6 is a section on the broken line 6-6 of Fig. 4, showing the valvein a different position, with parts of the construction broken away.

Fig. 7 is a section substantially on the line 11 of Fig. 5.

Fig. 8 is a partial section on the line 8-8 of Fig. '7.

Fig. 9 is ase'ctional plan view through a casing of an auxiliarysolenoid mechanism, showing the mechanism therein and illustrating partof the main casing in elevation and omitting part of the structure.

Fig. 10 is a sectional view through the structureshown in Fig. 9, thesection being substantiallyon the line l0-l ll of Fig. 11'.

the lower wall of the workpiece. time given above are examples of themany uses 2 Fig. 11 is a section substantially on the line Hll of Fig.10.

Fig. 12 is a diagrammatic view of the several mechanisms of theapparatus, indicating the wiring diagram and the switch controlmechanism; and

Fig. 13 is a view looking in the direction of the arrowv l3 of Fig. 1,showing the upper portion of the valve casing, and part of the solenoidmounting thereon.

In machines or apparatus of various kinds and classes, it has beendesirable to employ means to control stroke motion of an operating partof the machine. For example, in a drilling machine, it is desirable tocontrol the stroke of a drill in drilling the depth of cut in aworkpiece, and at the same time, to control speed of motion of the drillthrough operation of an air cylinder. In certain uses of the controlapparatus, it is also desirable to operate, for example, a tool at arelatively high speed in one predetermined move ment of the tool andthen to check or retard the motion of the tool in one period of thecycle of operation. To illustrate, in operating a drill, through aworkpiece when the drill is to pass through the full depth or thicknessof the workpiece, it is desirable to slow the speed of the drill feed asand when the drill is about to pass through The illustrato whichapparatus of the kind under consideration can be applied.

In the several views, Figs. 1 to 11 inclusive, all wiring has beeneliminated for sake of clarityin the showing, and in Fig. 12, the wiringdiagram is shown to illustrate the electrical means of the apparatus. Inthis figure, the several parts of the apparatus and the switch controlsthereof are shown diagrammatically.

.In practice, I provide a suitable frame or housing for support of myimproved control apparatus in conjunction with a machine of any type orkind. This frame or housing is generally identified by the referencecharacter 20, and includes a mounting end portion, part of which isshown at 2|, and a box-shaped casing part 22, in which the cylinder 23,two solenoids 2425 and the control valve mechanism 26 are arranged, aswill appear from a consideration of Figs. 1 to 3 inclusive of thedrawing. At one side of the casing 22 of the frame 20, is a supplementalcasing 21 in which a supplemental or auxiliary solenoid 28 is arranged.

The cylinder 23 in the construction shown, comprises a tubularmember 29,note Fig.3, to

the ends of which are secured upper and lower end plates 36-3l, theseplates being bolted together by four corner bolts 32, two of which areshown in Figs. 1 and 9 of the drawing. The end plate 36 has an intakeport 33 which also acts as an exhaust, whereas the end plate 3| has asimilar port 35. Slidably mountedin the plate 3 l, and suitably sealedtherein, is a piston rod 35, carrying at its upper end, a suitablecomposite piston structure 35. The rod 35 externally of the piston maybe coupled with any type or kind of tool or any mechanism of a device,actuation of which is to be controlled by the apparatus.

Noting Fig. 12 of the drawing, it will appear that an arm 37 is coupledwith the rod 35, the arm being freely guided in an extension 38 on theframe 23, through a guide finger 39.

The valve casing 26 is suitably supported on two of the bolts 32 andarranged within the frame or the casing 22 thereof. Fixed within atransverse bore 46 of the valve casing 26, is a sleeve or bushing 6| inwhich a valve 62 is mounted for rotary reciprocating motion. The valvehas'trunnion ends 4364 to which are secured gears 65-46, as clearly seenin'Fig. 4 of the drawing. The valve casing 26 has a single air admissionport 41, which may be termed the intake. A pipe 48 is coupled with thisport, and with which an air line from a source of high pressure airsupply is adapted to be connected. This supply is not shown, as itis'well known in the art.

The port 41 opens into two branches 46-56, as will clearly appear from aconsideration of Fig. 4 of the drawing, and communicating with thesebranches, the sleeve or bushing 6| has registering ports l52. Directlyopposed to the ports 5 l52, the sleeve or bushing has other ports 53-56,the latter opening into a horizontal port 5", with which a vertical port56 communicates, the port 55 being plugged, as seen at 5?, note Fig. 6.The port 53 opens into a horizontal port 58, with which communicates adownwardly extending port 53, the port 53 being also plugged, as seen at66.

The port 59 is placed in communication with the intake passage 36 at thebottom of the cylinder through a series of pipe or tube fittings, as at6!, note Fig. l of the drawing, so that air under pressure admitted tothe ports 53, 53 and 59 will extend to and enter the lower end of thecylinder 29 to move the piston 36 upwardly, thus this will be regardedas the upstroke. All reference to up and down is with respect to showingin the accompanying drawings, itbeing understood that the apparatus canbe mounted in any desired position.

Coupled with the passage 56 are pipes and fittings, generally identifiedas 62, in Fig. 1 of the drawing to place the port 56 in communicationwith the intake exhaust 33 at the upper end of the cylinder, so that inthe discharge of air under pressure from the ports 54 and 55, will bedirected through th pipes and fittings 62 to the port 33, causing thepiston 36 to move downwardly in the cylinder 23. To control the upwardand downward stroke movement of the piston 36, the valve 52 is givenrotary oscillatory movement in order to place the ports 5! and 53 and 52and 54 in communication. The valve 42 has two sets of substantiallyY-shaped passages, one of which is clearly shown in section in Fig. 6 ofthe drawing. These passages will be generally identified by thereference characters 63 and 64, the passage 64 being shown in transversesection in Figs. 3 and 6 ofthe drawing. The passage 63 is shown indotted lines in its relationship to the passage 64, in Fig. 6. Thepassage 63, in Fig. 6, is shown in position placing the passages 5i and53 in communication, thus admitting air, under pressure, to pass intothe passage '59 and thus into the lower end of the cylinder 29 to movethe valve into raised position. When the passage 63is in the positionshown in Fig. '6, the passage 64 is in position exhausting air from theupper end of the cylinder by placing passages 55 and 54 in communicationwith an exhaust passage 65 in the sleeve or bushing 4|, and registeringwith an exhaust passage 66 in the valve casing 26, as clearly seen 'inFig. 6 of the drawing. Another exhaust passage 61 is arranged in thesleeve or bushing 4| and registers with another exhaust passage 68 inthe casing 26.

The passage 66 registers with a horizontal passage 69 in which anadjustable needle valve 16 is arranged, and another adjustable needlevalve H is arranged ina similar passage'l2-which communicates with thepassage 66 through-a vertical passage 73. Another horizontal passage 14is disposed above the passage 12 and also-opens into the verticalpassage 13 and an automatically actuated sliding needle valve 15 isarranged in the passage 14, the valve 15 operating in a suitablestuifing box 16, note Fig. -8. Both passages 69 and 12 are placed incommunication through a passage ll, note Fig. 7, and register'with acommunication exhaust 18, with which a pipe 194s connected, and thispipe may extend to any suitable position.

From the foregoing, it-will be apparent that when the Y--shaped port isin the full lines position shown in Fig. 3 of the drawing, the companionport 63 is in the exhausting position, so as to exhaust air from thebottom of the cylinder as the piston 36 is being moved downwardly by airunder pressure passing through the ports 5264 and 56-55 and thus intothe port 33, as will be apparent. Considering Figs. 6, 7, and 8 of thedrawing, it'will be apparent that, many of the ports are shown asplugged at their outer ends and no specific description will be given ofthis structure as it is purely a mechanical expedient in showing themannerof forming and intercommunicating the separate portsand passagesthrough the valve.

To control operation of the valve 42,- the solenoids 24 and 25 areemployed, the cores of these solenoids terminating at their'lower endsin racks 39-6l, which are slidably mounted in the valve casing 26, andoperate in connection with the gears 45-46 respectively. One of theseracks and its engagement with the companion gear is clearly shown inFig. 5 of the drawing. In the construc-. tion shown, each core hasanenlarged-forked end, one of which is indicated at 82, in Fig. 5 of thedrawing and the racks are coup-led with the core through the medium of apin'33, The hanging or mounting of each rack 366 lis the same, exceptthat one rack is disposed at one side of theaxis of the valve 42 and theother on the opposite-side, as will appear from a consideration of Fig.4 of the drawing. Both racks are in constant engagement with theirrespective gears, and a balanced effect is provided, inthat upwardmovement of one rack-automatically transmits downward-movement to theopposed rack. In other words, as each solenoid is electrically actuated,its core is drawn upwardly to transmit one rotary motion to the valve,andthe other solenoid will reverse these rotary actions,'thus moving thevalves from theposition showniniFig 3, to:that

shown-in Fig. 6, in the two stages of operation of the'apparatus. Theforked ends of thecore include-a cross-head portion 84,. one of which isshown in end elevation in Fig.v 5, and these cross heads striking thelower portions of the solenoid windings, limit and check upward strokemovement of each core and correspondingly, the movement of the racks. Itwill thus be apparent that drilling of the ports in the valve will bemade preferably in assemblage of the valve and by movement of the racksand cores to the limit of their upward movement, as will be apparent.In-this way, positive registration and timing will be-provided.

.Considering Fig. 4.- of the drawing it will appear that'the bore 49 isclosed and sealed by suitable end plates 8586, thus providing a seal forlubrication in operation of the valve mechanism. It is also desirablethat the fit of the valve 42 in the bushing 4| be extremely snug, so asto prevent any possible air leakage.

The needle valves Hl1l extend outwardly through the casing 22 and haveknurled heads HY-4| by means of which these valves may be manuallyadjusted to control air flow through the respective exhaust passages,and thereby control speed of actuation of the piston 39 in the initialup and down movement thereof. For illustrative purposes, the downmovement may be said to be the feed movement, and thus the feed of atool to be actuated by the mechanism in engagement with a workpiece canbe controlled by regulating the exhaust of air from the lower end of thecyllnder23. Means is also provided in this down or feed stroke toprovide-what might be termed a delayed action or slower feed motion,which is accomplished through the sliding needle valve which is adaptedto choke-off the passage 13 immediately above the needle '52, as willclearly appear from a consideration of Fig. 8 of the drawing. Thislatter control is an auxiliary control, and thus may or may not beemployed in different types and kinds of work. However, the solenoid 28is provided for control "of the needle valve 15. The core of thesolenoid 28 has a cross head 8?, generally similar to the cross head 84.To this crosshead is attached a depending arm 38, with which'isadjustably coupled an actuating rod 89 having a head 99 which is adaptedto strike against a head 9! at the outer end of the-needle valve 15. Aspring 92 normally urges the rod 15 outwardly, or in other words,supports the same in inoperative position, and this spring also retainsthe solenoid core in an inoperative position. However, when the solenoid28 is energized, the core isdrawn inwardly, moving the cross head 8'!'to the'right,'as' seen in Fig. 11, correspondingly moving the rod 89and the needle valve '15. It will be understood that the adjustment ofthe rod 89 will control the degree of inward movement of the needlevalve in controlling the degree of choking the port 73. In Fig. 8 of thedrawing,

the valve lii may be said to assume a partially springs have beenomitted from the other showlngs for sake of clarity.

Turning now to the diagrammatic illustration of Fig. 12 of the drawing,here certain parts of the control mechanism are indicated in outlineform, together with the wiring diagram. On the arm 31 is arranged anadjustable trip finger 95 adapted to actuate a micro or other switch 96in circuit with the solenoid 24, so that as the piston 36 reaches apredetermined up position, the switch 96 will close the circuit to thesolenoid 24, causing the rack to move upwardly and the rack 8|downwardly, thus moving the valve 42 into the position shown in Fig. 3,allowing air to be admitted to the upper end of the cylinder'for downmovement of the piston 36. Also carried on, and by the arm 31, is ascrew rod 91 having adjustable trip nuts 98 r adapted to I operate aswitch actuator sleeve 99 slidably mounted in the extension 38 of theframe. A spring I99 normally supports the sleeve 99 in raised position.However, as the piston 36 moves downwardly, the nuts 98 will strike theupper end of the sleeve and start downward movement of the sleeve. Theinstant this movement takes place, another micro or other switch IOIwill be actuated through movement imparted through a switch actuator 12which is moved by the bevelled surface I93 on the sleeve. If the switch93 is in closed position, the solenoid 28 will be operated to move theneedle valve I5 into its control position. thus retarding the speed ofdownward movement of the piston 36.

Upon completing the desired downward stroke, another bevelled surfaceH14 on the sleeve will strike a pin 195, operating this pin toactuateanother micro or other switch I96 which will close the circuit to thesolenoid 25, causing the rack 8| to be moved upwardly, thus moving thevalve 42 to the position shown in Fig. 6. In this latter position of thevalve 42, air is admitted into the.

cylinder in the up and down movement of the piston, the speed at whichthe piston travels in the cylinder is controlled, the heads 10'--1I'being accessible for manual adjustment at all times.v

It will also be understood that the showing in Fig.

12 with respect to the sleeve 99 and the mecha-- nisms associatedtherewith is purely diagram-v matic and illustrates generally the ideaof a twostep or two-station control, the relative distances of travelbetween the stations may be varied. However, in such work, as control ofthe operation of a drill, the control of last stages of drill operationare relatively slight and this type of illustra tion is diagrammaticallyshown in Fig. 12.

While the circuit wiring is quite apparent, it might briefly bedescribed in stating that wires HIT-I08 represent a source of electricalsupply. The circuit to the solenoid 24 is controlled through branchesI09, leading to the switches 99, I ID from the switch to the solenoidand I l I from the solenoid to the wire I08. The circuit to the solenoid25 is controlled by the wire I I2 extending to switch I06, while thewire H3 from the switch I06 extends to the solenoid 25 and wire H4 fromthe solenoid to the wire I 08. Circuit to the solehoid N ls-controlledby wire H 'leadingrto: switch I0 I, then through wire I lfi fromswitch.I.0.l.:to: the solenoid- 28 through switch 93 and then by. wire H! fromsolenoid 2-8 to wire 38;

I Fig. 13 has been shown in order to illustrate the mounting of thesolenoids upon the upper portion of the valve-casing 26. This valvecasing has-at-its ends, upwardly extending lugs H3 and a center lug l 19with whichare coupled upwardly extendingmetal straps, all indicated bythereference-character E29. To these straps'are attached the sidemembers of the U-shaped frames 2425- of thesol'enoidsZA-JE. Alsoillustrated in Fig. 13, is the forked-end 82' of the core ofth'esolenoid 24, as'wellas thecross head-8 t. The cross head 8% is in theraised position, whereas the-cross head 84i-s in the lowered position,thus in Fig. 13, the rack-86 is in the raised position and the rackBl inthe lowered position. The straps I20 guide the cross heads in theirmovements; At'83 is-shown the pin which couples the rack 88 with theforked portion B2 of the crosshead84';

By providing the balanced action between the solenoids 2E25 and themechanism thereof, the apparatus can be mounted and utilized 'inanyposition without danger of faulty operation due to unbalanced conditionsof the operating part. Furthermore, this balance provides an ease ofaction in actuation'of the valve. The total rotary oscillating motion ofthe valve is between the two positions shown inFigs. 3 and 6 and byproviding the wide type'passages (W-66, automaticmovement from theintake to exhaust positions is provided; one passage of the valveexhaustingwhile the other passage is in the intake position. It willalso be apparent that a very compact control, unit'or apparatus isprovided which may be readily attached to'or mounted in conjunctionwithmachinesof any type or kind incontrolling operation of a predeterminedmember of the machine or a tool driven by the machine.

Having fully described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. An apparatus of the character described comprising an air cylinder, apiston operating in the cylinder and including an operating rodextendingthrough one end of the cylinder, a'val've controlling admissionof air under pressure to opposed ends of the cylinder and the exhaust ofairfrom said ends of the cylinder, said valve being arranged in a valvec'asing,ggears on opposedends' of saidvalve within said casing, a'pairof racks slidably mounted in the ends of the casing and operativelyengaging said gears for imparting rotary'reciprocating motion to thevalve, means 'adjustable in the casing controlling the speed of travelof the piston in the cylinder in both directions, and a pair ofsolenoids for'operating said racks in controlling operation ofsaid'valve.

2. An apparatus of the character, described comprising an air cylindenapiston operating-in the cylinder and-including anoperatingrodextending'through one end of the cylinder, a valve controlling admissionof air under pressure to opposed ends of the cylinder and the exhaust'ofair from said ends of the cylinder, said valve being;

arranged in a-valve casing, gears on opposed ends of said valve withinsaid casinga pair'of racks slidably mounted in the ends of the casingandoperatively engagingsaid; gears for imparting rotary reciprocatingmotion to the-valve,- means adjustablein the casing controlling the,speed of' travel ofjthe piston in the cylinder in both directions; apair ofsolenoids for operating'saidracks' in controlling: operation: ofsaidvalve,andiadjuste able; meansin circuit. with; said. solenoidscontrolling the: stroke of the piston in:the cylinder..

3.. An. apparatus .of the. character described comprising. an air'cylinder, a piston operating .in the. cylinder and including .an.operating rod ex tending throughone end of the. cylinder, .a valvecontrolling admission of air under pressure to opposedends of thecylinder. and the exhaust. of air from said'endsof the cylinder, saidvalve being arranged in avalve casing, gears on opposed. ends of. saidvalve withinsaidi casing, apair of racks slidably mountedin. the: ends.ofv the casingiand operatively engaging said gears forimpartingrotaryreciprocating'motion to the:valve,,.means.adjustable inthexcasing controlling the. speed; of travel of thepistonin the cylinderin. both direce tions, a pairv of:solenoids.ior operatingsaidracks incontrolling, operation of said valve, adjustable meansv in circuitwithlsaidi solenoidsv controlling the stroke of thepistonin'the'cylinder, and means comprising another movable elementin-the valve casing for varying thev speed of travel of the piston inthe cylinder in one stroke motion thereof.

4. An apparatus of. the character described comprising anair cylinder,a; piston operating. .in the cylinderan'd includingan-operatingrodextending through oneend of thecylinder, a valvecontrolling admission ofv air under pressure to opposed ends of thecylinder and. the exhaustof air from said ends of the cylinder, saidvalve being arranged in a valve. casing, gears. on opposed ends of saidvalve within said casing, a pair. of racks slidably mounted in theends:of the casing and operatively engaging said gears for impartingrotaryreciprocating motion to the va1ve,,meansad.- justablev inthe casingcontrolling the speed .of travel of the piston in thecylinder in bothdirections, a pair of solenoidsfor operating said racks in controllingoperation of said valve, adjustable means in circuit with said solenoidscontrolling the. stroke of the piston in the cylinder, means comprisinganother movable elementin the valve casing for. varying the speed oftravel of the piston in the cylinder in one stroke motion thereof, and asolenoidcontrolling.the, operation of said last named element.

5. In drivecylinders of the character described, acontrol valve,saidvalvelcomprising a casing,.a bushing, in said casing. having fixedvports communicating with intake and discharge passages in the valvecasing, a valve mounted in the bushing and having passages adaptedjtoregister with intake and discharge passages of the bushing and casing,the valve havinggears, at end portions thereof, racks slidablymountedfin thecasing and operatively engaging said. gears, said gearsand racks being adapted to impart-rotary reciprocating motion to thevalve in movingthe ports thereof' into intake and exhaust positions, apair'of solenoids on the valve casin and coupled with said racks foractuating the valve, and automatically actuated means controllingoperation of the solenoids in controlling operation of a piston'in thedrive cylinder in both directions.

6. In'drive cylinders of the character described, a control valve, saidvalve comprising a casing, a bushing in said casing having fixed portscommuni-cating with intake and'discharge passages in the valve casing, avalve mounted in the bushing and having passages adapted to registerwith intake and discharge passages of the bushing and casing; the valvehaving gears at end portions thereof, racksslidably mounted in thecasing and operativelyengaging said gears, said gears and racks beingadapted to impart rotary reciprocating motion to the valve in moving theports thereof into intake and exhaust positions, a pair of solenoids onthe valve casing and coupled with said racks for actuating the valve,automatically actuated means controlling operation of the solenoids incontrolling operation of a piston in the drive cylinder in bothdirections, the intake and exhaust passages being arranged in twoseries, and the valve having two ported sections operatively engagingthe series of ports in control of the intake and exhaust of saidcylinder.

7. In drive cylinders of the character described, a control valve, saidvalve comprising a casing, a bushing in said casing having fixed portscommunicating with intake and discharge passages in the valve casing, avalve mounted in the bushing and having passages adapted to registerwith intake and discharge passages of the bushing and. casing, the valvehaving gears at end portions thereof, racks slidably mounted in thecasing and operatively engaging said gears, said gears and racks beingadapted to impart rotary reciprocating motion to the valve in moving theports thereof into intake and exhaust positions, a pair of solenoids onthe valve casing and coupled with said racks for actuating the valve,automatically actuated means controlling operation of the solenoids incontrolling operation of a piston in the drive cylinder in bothdirections, the intake and exhaust passages being arranged in twoseries, the valve having two ported sections operatively engaging theseries of ports in control of the intake and exhaust of said cylinder,and adjustable means on the valve casing controlling the exhaust fromthe cylinder in controlling the drive action of the piston in thecylinder.

8. In apparatus employing a drive cylinder for controlling the feed andoperation of a tool or the like, a piston in said cylinder, the opposedends of the cylinder having means for admitting and discharging apressure medium in the drive of the piston in both directions in thecylinder, a valve casing, an intermittently reciprocating valve in saidcasing, means slidably mounted in said casing for actuating said valve,automatically actuated electrical means for actuating said last namedmeans for controlling intake and discharge of the pressure medium withrespect to opposed ends of the cylinder by movement imparted to saidvalve, means comprising manually adjustable devices controlling thecircuit to said electrical means for actuating said valve to controltravel of the piston in said cylinder in both directions, manuallyadjustable means in the valve casing controlling discharge of thepressure medium from both ends of the cylinder in controlling speed oftravel of the piston in both directions in the cylinder, a pair of gearsand racks for actuating said valve, and said electric means comprising apair of solenoids actuating said racks.

9. A valve mechanism comprising a casing having ports, a valve rotatablymounted in said casing and having two sets of ports for registering withthe ports of said casing, a gear and rack structure at each end portionof said casing, each gear and rack being adapted to impart rotaryreciprocating motion to the valve in moving the two sets of ports of thevalve into predetermined positions of registration with the ports ofsaid casing, and means simultaneously operating said racks in oppositedirections in the rotation of said valve.

10. A valve mechanism comprising a casing having ports, a valverotatably mounted in said casing and having two sets of ports forregistering with the ports of said casing, a gear and rack structure ateach end portion of said casing, each gear and rack being adapted toimpart rotary reciprocating motion to the valve in moving the two setsof ports of the valve into predetermined positions of registration withthe ports of said casing, means simultaneously operating said racks inopposite directions in the rotation of said valve, and means adjustablein the casing controlling the area of predetermined ports therein.

GEORGE W. EMRICK.

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